This research proposes to investigate specifically the neural reflexes involved in regulation of the pattern of breathing and of laryngeal aperture in awake humans with respect to adaptation ot mechanical loads. The contribution of perceptual reactions to mechanical loading, an unavoidable and significant contaminant of the neural reflex responses using traditional experimental techniques, will be eliminated by using a new loading technique, which permits the reliable assessment of pattern responses to external flow resistive and elastic loads that are imperceptible to the subjects. A major goal of this research is to identify those aspects of the pattern, measured mechanically (airflow) or electrically (diaphragmatic EMG), that can be used to estimate neural reflexes to loading, free of mechanical artifact and the influence of intrinsic muscle properties. Influence upon these neural reflex responses to loading of mental alertness, of loading via mouth or body surface, of alteration in chest wall afferent information, of changes in the end-expiratory lung volume, and of changes in baseline respiratory mechanical impedance will be examined. Laryngeal aperture responses to loading will be investigated under similar experimental conditions in order to determine control strategies that may be used inrregulating this accessory organ of respiration. These studies will assess possible laryngeal roles in respiratory pattern accomodation to mechanical loading, as well as in control of the end-expiratory volume. An automated analysis technique will be developed to facilitate the measurement of these aperture responses to imperceptible loads. Influences upon the control of the aperture of perceptual reaction to perceived loads and of changes in the end-expiratory volume will be determined. These studies involve measurement of respiratory responses to small alterations in external loading of magnitude similar to those encountenred normally due to changes in internal mechanics. These results will indicate the capability of neural reflexes to provide compensation to mechanical loads through both pattern and laryngeal aperture responses in the normal human and will provide a basis for judging any influence of pathology upon these responses.